Document Detail

Identification of Salmonella enterica serovar Typhimurium genes important for survival in the swine gastric environment.
MedLine Citation:
PMID:  16597989     Owner:  NLM     Status:  MEDLINE    
Since the stomach is a first line of defense for the host against ingested microorganisms, an ex vivo swine stomach contents (SSC) assay was developed to search for genes important for Salmonella enterica serovar Typhimurium survival in the hostile gastric environment. Initial characterization of the SSC assay (pH 3.87) using previously identified, acid-sensitive serovar Typhimurium mutants revealed a 10-fold decrease in survival for a phoP mutant following 20 min of challenge and no survival for mutants of rpoS or fur. To identify additional genes, a signature-tagged mutagenesis bank was constructed and screened in the SSC assay. Nineteen mutants were identified and individually analyzed in the SSC and acid tolerance response assays; 13 mutants exhibited a 10-fold or greater sensitivity in the SSC assay compared to the wild-type strain, but only 3 mutants displayed a 10-fold or greater decrease in survival following pH 3.0 acidic challenge. Further examination determined that the lethal effects of the SSC are pH dependent but that low pH is not the sole killing mechanism(s). Gas chromatography analysis of the SSC revealed lactic acid levels of 126 mM. Upon investigating the effects of lactic acid on serovar Typhimurium survival in a synthetic gastric fluid, not only was a concentration- and time-dependent lethal effect observed, but the phoP, rpoS, fur, and pnp genes were identified as involved in protection against lactic acid exposure. These studies indicate a role in gastric survival for several serovar Typhimurium genes and imply that the stomach environment is defined by more than low pH.
Shawn M D Bearson; Bradley L Bearson; Mark A Rasmussen
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  72     ISSN:  0099-2240     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2006 Apr 
Date Detail:
Created Date:  2006-04-06     Completed Date:  2006-06-28     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2829-36     Citation Subset:  IM    
US Department of Agriculture, Agricultural Research Service/NADC, 2300 Dayton Ave., Ames, IA 50014, USA.
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MeSH Terms
Bacterial Proteins / genetics*,  metabolism
DNA Transposable Elements
Gene Expression Regulation, Bacterial
Hydrogen-Ion Concentration
Lactic Acid / pharmacology*
Salmonella typhimurium / drug effects,  genetics,  growth & development*
Stomach / microbiology*
Swine / microbiology*
Reg. No./Substance:
0/Bacterial Proteins; 0/DNA Transposable Elements; 50-21-5/Lactic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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